AP Biology  Chapter 6 and 7  Tour of the Cell  Membrane Transport

Eukaryotic cell’s genetic instructions  Nucleus  Nuclear envelope  Nuclear lamina  Chromosomes  Nucleolus

Eukaryotic cell ribosomes  Ribosomes  Free ribosomes  Bound ribosomes

Endomembrane system  Nuclear envelope  ER  Golgi apparatus  Lysosomes  Plasma membrane  Vesicles  Vacuoles

Endosymbiosis Theory

Mitochondria  Mitochondria  Cristae  Mitochondrial matrix

Chloroplasts  Thylakoids  Granum  Stroma  plastids

Peroxisomes

Cytoskeleton  Network of fibers extending throughout the cytoplasm  Roles of cytoskeleton  Mechanical support to cell shape  Cell motility (movement) using motor proteins

Cell junctions  Tight junctions- plasma membrane of other cells form a seal which prevents leakage

Cell Junction  Desmosomes (anchoring) Fasten cells together into strong sheets

Cell Junction  Gap Junction- provide cannels so cells can communicate with each other, and molecules can pass to and from

AP Biology- Quiz today  Finishing extracellular components

Cell wall parts of plant  Cell wall- protects and maintains shape  Primary cell wall- thin flexible wall (young plant)  Secondary cell wall- hardened structure between the plasma membrane and primary wall  Middle lamella- Thin layer with sticky polysaccharides (pectins) glues cells together  Plasmodesmata- communicating channel between plant cells

Chapter 7- Membranes  The plasma membrane separates the living cell from its surroundings  Selectively permeable: some substances cross more easily than others  Membrane encloses a solution different from the surrounding solution

Phospholipid bilayer  Contains: lipids, proteins, and carbohydrates  Most abundant lipid: phospholipid  Amphipathic molecule: hydrophilic and hydrophobic regions

Phospholipid Bilayer  Fluid mosaic model: the membrane is a fluid structure with various proteins embedded in or attached to the double layer

Phospholipid bilayer 1. Not all membranes are like  Membranes with different functions differ in chemical composition and structure 2. Measurements showed that membrane proteins are not very soluble in water

Phospholipid bilayer  Freeze fracture technique  Splits a membrane along the middle of the phospholipid bilayer  Found that: membranes are more mosaic than fluid, lipids appear to form defined regions

Phospholipid Bilayer  Membrane molecules are held in place by relatively weak interactions  Most lipids and some proteins drift laterally in the plane of the membrane but rarely flip-flop from one phospholipid layer to the other

Phospholipid bilayer  Membrane fluidity is influenced by temperature:  As temperature cools, membranes switch from a fluid state to a solid state  Phospholipids pack together more closely

Phospholipid bilayer  Steroid cholesterol is wedged between phospholipid molecules in the plasma membrane of animal cells  Warm temp: restrains movement (reduces fluidity)  Cold temp: maintains fluidity by preventing tight packing  Fluidity buffer

Proteins determine membrane’s function  Two major populations of membrane proteins: integral and peripheral

Membrane Proteins  Integral-  Embedded in the bilayer  Penetrate hydrophobic interior of bilayer  Peripheral-  Not embedded in the bilayer  Loosely bound to surface of membrane

Major functions of membrane proteins 1. Transport 2. Enzymatic activity 3. Signal transduction (relaying messages) 4. Cell-cell recognition 5. Intercellular joining 6. Attachment to cytoskeleton

 Cell to cell recognition- ability of a cell to distinguish one type of neighboring cell from another  Membrane carbohydrates may be bonded to lipids or proteins making glycolipids or glycoproteins respectively

 Selective permeability and structure: 1. Small molecules and ions move across the plasma membrane in both directions Example:  sugar, amino acids and other nutrients enter a muscle cell and metabolic waste leave  The muscle cell takes in oxygen and expels carbon dioxide  Muscle also regulates the concentrations of inorganic ions, such as Na, K, Ca, Cl by shuttling them one way or the other across the membrane

 Movement of molecule depends on the interaction of the molecule with the hydrophobic interior of membrane  Nonpolar molecules can dissolve in the lipid bilayer easily  Polar molecules and water extremely small can cross bilayer slowly  Passage of water occurs via aquaporins  Carrier proteins- bind to molecules and change shape to shuttle them across membrane

Membrane Transport Passive Transport DiffusionOsmosis Tonicity IsotonicHypertonic Hypotonic Facilitated Diffusion Carrier proteins Channel proteins Active transport Sodium- potassium pump Cotransport Vesicular Transport ExocytosisEndocytosis PinocytosisPhagocytosis Receptor- mediated endocytosis

Water potential  A property predicting the direction in which water will flow  Formula:  Ψ = Ψ S + Ψ P

Water Potential  Ψ S = -iCRT  i = ionization constant (1 for sucrose)  C = osmotic molar concentration  R = Pressure constant (R= liter bars/mole °Kelvin  T = temperature

Calculations:  Calculate the osmotic potential using the following data. Answer should be in bars.  C = 0.32  T =21 °C *must convert to Kelvin